In an optical assembly such as an optical fiber communications system, a light beam is transmitted through an optical fiber. There are many situations where the light beam is extracted from the optical fiber so that it passes through free space, is processed with a discrete optical device, and then is re-introduced into a second optical fiber. The termination of the optical fiber that allows the light beam to be extracted from the optical fiber in a controlled manner, or reintroduced into the second optical fiber, is an optical collimator. Optical collimators are well known and widely used in the art.
The alignment between the optical collimator and the optical device is often critical to the successful operation of the optical assembly. A misalignment may prevent the successful operation of the optical device, as in the case of a thinfilm optical filter that achieves the proper light filtering only for a narrow range of the angle of incidence of the light beam. A misalignment may also result in an excessive attenuation of the light beam, so that cumulatively over a number of extractions and re-introductions the light beam loses its signal strength.
The optical collimator has a collimator beam-path axis, to which the optical device must be aligned. The alignment must be maintained over extended periods of time in service, during which time the optical assembly may be subjected to temperature changes, vibration, and adverse environmental influences. In a conventional fabrication approach for aligning the optical collimator and the optical device, the end of the optical collimator and the optical device are first carefully aligned. While the alignment is maintained, the end of the optical collimator and the optical device are bonded in a face-to-face relation using an optical adhesive positioned between the optical collimator and the optical device. The optical assembly is fabricated by using the same technique at each of the collimator/optical device interfaces.
While this approach is operable, the present inventor has recognized that it has several drawbacks. The alignment and bonding are difficult to achieve due to the small sizes of the components and the high degree of precision that is required. A great deal of skill is required in the assembler, and in any event the process is tedious and time-consuming. The process often has low yields of operable optical assemblies, particularly when there are a number of optical collimator/optical device interfaces in the optical assembly. Additionally, there is a layer of optical adhesive lying in the beam path between the collimator and the optical device. Optical adhesives having excellent optical properties are known and are used, but even the best available optical adhesives may change their properties over extended periods of time in service. Consequently, the optical and mechanical properties of the optical joint between the optical collimator and the optical device may change over time.
There is therefore a need for an improved approach to establishing the interface between an optical collimator and an optical device. The present invention fulfills this need, and further provides related advantages.